Co-targeting of endothelin-A and vitamin D receptors: a novel strategy to ameliorate cisplatin-induced nephrotoxicity

Endothelin system expression in the kidney following cisplatin-induced acute kidney injury in male and female mice

The chemotherapeutic agent cisplatin accumulates in the kidney and induces acute kidney injury (AKI). Preclinical and clinical studies suggest that young female mice and women show greater recovery from cisplatin-AKI compared to young male mice and men. The endothelin (ET) and ET receptors are enriched in the kidney and may be dysfunctional in cisplatin-AKI; however, there is a gap in our knowledge about the putative effects of sex and cisplatin on the renal ET system. We hypothesized that cisplatin-AKI male and female mice will have increased expression of the renal ET system. As expected, all cisplatin-AKI mice had kidney damage and body weight loss greater than control mice. Cisplatin-AKI mice had greater cortical Edn1, Edn3, Ednra, and Ednrb, while outer medullary Ednra was significantly suppressed in both sexes. Of the ∼25 000 genes sequenced from the inner medulla, only 91 genes (comparing saline mice) and 134 genes (comparing cisplatin-AKI mice) were differentially expressed and they were unrelated to the ET system. However, Edn1 was significantly greater in the inner medulla of male and female cisplatin-AKI mice. Thus, RNA profiles of the ET system were significantly affected by cisplatin-AKI throughout the kidney regardless of sex and this may help determine the therapeutic potential of targeting the ET receptors in cisplatin-AKI.

A Canadian Study of Cisplatin Metabolomics and Nephrotoxicity (ACCENT): A Clinical Research Protocol

Background:

Cisplatin, a chemotherapy used to treat solid tumors, causes acute kidney injury (AKI), a known risk factor for chronic kidney disease and mortality. AKI diagnosis relies on biomarkers which are only measurable after kidney damage has occurred and functional impairment is apparent; this prevents timely AKI diagnosis and treatment. Metabolomics seeks to identify metabolite patterns involved in cell tissue metabolism related to disease or patient factors. The A Canadian study of Cisplatin mEtabolomics and NephroToxicity (ACCENT) team was established to harness the power of metabolomics to identify novel biomarkers that predict risk and discriminate for presence of cisplatin nephrotoxicity, so that early intervention strategies to mitigate onset and severity of AKI can be implemented.

Objective:

Describe the design and methods of the ACCENT study which aims to identify and validate metabolomic profiles in urine and serum associated with risk for cisplatin-mediated nephrotoxicity in children and adults.

Design:

Observational prospective cohort study.

Setting:

Six Canadian oncology centers (3 pediatric, 1 adult and 2 both).

Patients:

Three hundred adults and 300 children planned to receive cisplatin therapy.

Measurements:

During two cisplatin infusion cycles, serum and urine will be measured for creatinine and electrolytes to ascertain AKI. Many patient and disease variables will be collected prospectively at baseline and throughout therapy. Metabolomic analyses of serum and urine will be done using mass spectrometry. An untargeted metabolomics approach will be used to analyze serum and urine samples before and after cisplatin infusions to identify candidate biomarkers of cisplatin AKI. Candidate metabolites will be validated using an independent cohort.

Methods:

Patients will be recruited before their first cycle of cisplatin. Blood and urine will be collected at specified time points before and after cisplatin during the first infusion and an infusion later during cancer treatment. The primary outcome is AKI, defined using a traditional serum creatinine-based definition and an electrolyte abnormality-based definition. Chart review 3 months after cisplatin therapy end will be conducted to document kidney health and survival.

Limitations:

It may not be possible to adjust for all measured and unmeasured confounders when evaluating prediction of AKI using metabolite profiles. Collection of data across multiple sites will be a challenge.

Conclusions:

ACCENT is the largest study of children and adults treated with cisplatin and aims to reimagine the current model for AKI diagnoses using metabolomics. The identification of biomarkers predicting and detecting AKI in children and adults treated with cisplatin can greatly inform future clinical investigations and practices.

Role of vitamin D/VDR nuclear translocation in down-regulation of NF-κB/NLRP3/caspase-1 axis in lupus nephritis

BACKGROUND

Vitamin D receptor (VDR) and NLRP3 inflammasome play critical roles in lupus nephritis (LN) pathogenesis.

AIM OF THE STUDY

This study explored the therapeutic effect of VDR agonist on LN and its molecular mechanism to inhibit NLRP3 signalling.

METHODS

C57BL/6 mice, lupus-prone MRL/lpr mice, and VDR agonist paricacitol-treated MRL/lpr mice (300 ng/kg/mouse per dose, 5 times/week for 8 weeks from 8 weeks old) were used to assess kidney histopathology and measure proteinuria, serum anti-ds-DNA antibody and expression of NF-κB/NLRP3/caspase-1/IL-1β/IL-18 axis. We used mouse renal tubular epithelial cells (mRTECs) to identify protein-protein interactions and examine the effects of paricalcitol.

RESULTS AND CONCLUSION

LN pathogenesis decreased after paricalcitol treatment. We observed a marked improvement in renal pathology and a time-dependent decrease urine protein and serum anti-dsDNA antibody levels. In 16-week-old MRL/lpr LN mice, the upregulated expression of NLRP3/caspase-1/IL-1β/IL-18 axis was significantly downregulated after paricalcitol treatment. Paricalcitol can reverse the apoptosis induced by anti-dsDNA antibody via the NF-κB/NLRP3/caspase-1/IL-1β/IL-18 axis in mRTECs. Furthermore, paricalcitol suppressed NF-κB nuclear translocation by competitively binding to importin-4. In summary, the VDR agonist can alleviate LN by modulating the NF-κB/NLRP3/caspase-1/IL-1β/IL-18 axis and suppressing the NF-κB nuclear translocation.

Vitamin D and Acute Kidney Injury: A Two-Way Causality Relation and a Predictive, Prognostic, and Therapeutic Role of Vitamin D

Background: Acute kidney injury (AKI) constitutes a multi-factorially caused condition, which significantly affects kidney function and can lead to elevated risk of morbidity and mortality. Given the rising scientific evidence regarding vitamin D's (VitD's) multisystemic role, the connection between AKI and VitD is currently being studied, and the complex relation between them has started to be unraveled.

Methods: A systematic review had been conducted to identify the pathogenetic relation of VitD and AKI and the potential role of VitD as a biomarker and therapeutic–renoprotective factor.

Results: From 792 articles, 74 articles were identified that fulfilled the inclusion criteria. Based on these articles, it has been found that not only can VitD disorders (VitD deficiency or toxicity) cause AKI but, also, AKI can lead to great disruption in the metabolism of VitD. Moreover, it has been found that VitD serves as a novel biomarker for prediction of the risk of developing AKI and for the prognosis of AKI's severity. Finally, animal models showed that VitD can both ameliorate AKI and prevent its onset, suggesting its renoprotective effect.

Conclusion: There is a complex two-way pathogenetic relation between VitD disorders and AKI, while, concomitantly, VitD serves as a potential novel predictive–prognostic biomarker and a treatment agent in AKI therapy.

Nuclear receptors in the kidney during health and disease

Over the last 30 years, nuclear receptors (NRs) have been increasingly recognized as key modulators of systemic homeostasis and as contributing factors in many diseases. In the kidney, NRs play numerous important roles in maintaining homeostasis-many of which continue to be unraveled. As "master regulators", these important transcription factors integrate and coordinate many renal processes such as circadian responses, lipid metabolism, fatty acid oxidation, glucose handling, and inflammatory responses. The use of recently-developed genetic tools and small molecule modulators have allowed for detailed studies of how renal NRs contribute to kidney homeostasis. Importantly, while NRs are intimately involved in proper kidney function, they are also implicated in a variety of renal diseases such as diabetes, acute kidney injury, and other conditions such as aging. In the last 10 years, our understanding of renal disease etiology and progression has been greatly shaped by knowledge regarding how NRs are dysregulated in these conditions. Importantly, NRs have also become attractive therapeutic targets for attenuation of renal diseases, and their modulation for this purpose has been the subject of intense investigation. Here, we review the role in health and disease of six key renal NRs including the peroxisome proliferator-activated receptors (PPAR), estrogen-related receptors (ERR), the farnesoid X receptors (FXR), estrogen receptors (ER), liver X receptors (LXR), and vitamin D receptors (VDR) with an emphasis on recent findings over the last decade. These NRs have generated a wealth of data over the last 10 years that demonstrate their crucial role in maintaining normal renal homeostasis as well as their capacity to modulate disease progression.